Question

There are so many helper external libraries which can be included into java project like Google Guava, Apache commons etc. What are the cons of including a lot of these and will it has an impact on the performance of project or is it a over kill.

Based on how much you want to use an external library decides if you want to include it in the project or not but other than that are there any other issues which needs to be thought about?

Answer 1

Loading a large number of libraries might eventually blow your permgen space (where class definitions are stored) and static methods/fields might potentially take a lot of memory even if you don’t use a certain class in a jar. In practice, though, this doesn’t usually become an issue, unless you are working with very constrained devices (e.g. embedded).

A different issue, however is that, with more libraries:

• it becomes harder to track what’s really needed and what not, i.e. maintainability
• you potentially open yourself to the vulnerabilities of each of those libraries
• the number of unknown variables increases in your project, which might result in unpredictable behavior or longer bug hunts

But there’s a fairly good chance that open source, long maintained libraries have considerably better quality than the stuff any of us writes on the first few versions.

In summary: keeping it all tidy and lean is a good thing, but do not implement code that a library would do for you simply to avoid including that library!

That said, I’m sure this has the potential of a war of opinions, so see what others say!